Transformer arrangement



Dec. 8, 1931. V Q AUSTIN 1,835,200

TRANSFORMER ARRANGEMENT Filed March 16, 1927 c 65. 3 INVENTOR. r MQ Q Byawz 1 e ATTORNEY$ Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY TRANSFORMER ARRANGEMENT Application filed March 16, 1927.

This invention relates to high tension transformer systems and has for one of its objects, the provision of an improved arrangement of transformers which will permit the production of a voltage equal to the sum of the separate voltages of the individual transformers and at the same time maintain as good regulation for the system as that of the individual transformers. A further ob ect is to provide an arrangement of transformers having a total power output substantially equal to the sum of the outputs of the several individual transformers. Further ob ects and advantages will appear from the following description. The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification and it is more particularly pointed out in the appended claims.

In the drawings- Fig. 1 is a diagrammatic view of one system of connections illustrating three transformers arranged according to one embodiment of the present invention.

Fig. 2 is a view similar to Fig. 1 showing a slightly modified arrangement.

3 is a view similar to Fig. 2 showing a further modification.

In testing or power transformers, particularly ones for the generation of high volages, there are three important considerations to be taken into account. One is the generation of a high voltage without excessive loss in the transformer. Another consideration is the regulation, or ratio of voltage at full load to that at no load. Another consideration is the power or kva. output of the transformer or combination of transformers.

One method of producing a high voltage has been by the well known chain or series connection where one transformer excites the next transformer. This form of connection is illustrated in U. S. Patent 1,523,367. \Vhile high voltage can readily be produced by this method it is open to the serious objection that the regulation is exceedingly poor and the power or kva. output 15 limited to that of the first transformer in the series. The poor regulation makes it exceedingly dif- Serial No. 175,654.

lieult to determine the voltage applied for test purposes and makes the transformer entirely unsuitable for power transmission. The low power output of the connected transformers considering the total kva. capacity is av serious objection from the economical standpoint.

In my imp roved method of connecting up and exciting the transformers the objections of the ordinary chain connection are practically eliminated. In an ordinary chain connection with each transformer having an output of 500 kw. or 500 kva., the total output for the chain connection could not exceed this value and the regulation also would be poor. lVith the improved method of connecting up shown in Fig. 1, the output of the three transformers, assuming each to have an output of 500 kw. or 500 kva., would be 1500 kva. and the regulation would be exceedingly good. lVhere the proper voltage and current capacities of the transformers exist, it is possible to develop the accumulative or total kva. capacity of all the transformers in the series. This is of great economic importance for where three transformers are used, the individual transforn'iers may, with my form of connection, each have only a third of the capacity required to develop the same kva. output where the old form of chain connection is used. Further than this, the regulation is greatly improved so that the ratio of the transformer is a much more accurate guide in determination of the high voltage. This is an advantage in running tests or in the transmission of power.

Fig. 1 shows one form of the connection which, however, may be modified considerably, depending on the degree of regulation and power output sought and upon the design of the transformers. Y t I evident that where one end of the high voitage winding is grounded a different set-up may be used, from that employed where the center of the high voltage winding is grounded, without materially changing the relation. In F ig. 1., there are three transformers A, B and C, having high tension windings 10, 11 and 12', the transformers being energized by alternators 16, 17 and 18 and 19 connected to suitable end turns by taps 20-21, 22 23,2 l25, 26-27, 2829, 30-31, in the high voltage windings. A turn at each end of the high tension windings 10, 11 and 12 is formed of a sufficiently heavy conductor so that these end turns may be excited to act as low tension windings by the use of separate generators. As shown, the low tension winding of each transformer is excited from a source of energyindependent of the load current flowing g T his differs from the ordinary chain connection of transformer in which the low tension windings of all of the transformers except the first in the series, depend upon the current flowing in the. high tension circuit for their excitation. p

It is evident that where all the generators in the high tension windings.

are in synchronism the transformers and generators will beheld in step or in proper phase relation. The connection between. end turns of adjacent transformers, while similar to that in the chain connection, produces a different operation under general conditions. In the chain connection, it is necessary that all magnetizing or power current be supplied from the generator exciting one of the transformers in the chain. In the improved arrangement, however, the exciting or magnetizing current for the various transformset-up and makes it possible to drive the gen erators by an simple means such as an insulated belt, rope or shaft. The generators may be driven by induction motors 13, 1 1,

15 and 15 as a difference in motor or belt slip will provide for keeping the transformers in. the proper phase relation. T he driving means should, of course, drive the several alternators at the same frequency under no load or full load conditions, to get the rest results. It is also evident that some economy may be effected in selecting the generators in accordance with the duty imposed upon them in the different locations or where the ratio or power output of transformers varies in the chain. I

In Fig. 1, all generators except 16 must, of course, be insulated from ground and from the cases of the transformers.

The respective generators 17, 18 and 19 may be set for the generation of definite voltages and the variation in voltage controlled by generatorlfi as this is at ground potential. If wide variation in voltage is desired, the insulated generators 17, 18 and 19 may have direct connected exciters whose voltage can be readily controlled by the operation of suitable rheost-ats 1?,18 and 19 respectively by means of an insulated rod or string 'or by fluid pressure through an insulated tube.

One very convenient way of controlling the Q voltage is to use storage batteries 16,", 17", 18" and 19" for exciting the generators. the voltage being controlled by varying'the re sistance in the battery or field circuit or the number of cells in the storage battery. The 75 battery can, of course, be easily insulated on th same support as the generator. One very satisfactory arrangement, where the highest tlgl;.-8 of regulation is not essential, is to use .l. f'nators 16 i and 18 only. It is evident that with the two alternatorsall exciting and magnetiziu current may be supplied direct f in the alternators without going through the chainof transformers.

l 2 shows a connection somewhat similar to that shown in Fig. 1. lnFig. 2, the; transformers D, E and F have high voltage windings 40, 41 and 42 with one endof each of the high voltage windings grounded to the transformer case. The transformers D, E and F are excited by generators 46,47, 48,1; and 49. l -Jith this arrangement, generator would seldom be used as this generator would have to be mountedon an insulated support having a high degree of insulation, and if supported from-the case of transform- F. would have to have sufficient insulation for the voltage generated in transformer F. With the arrangement shown, and generator 49 omitted, itis possible to mount the gencraters 47 and 48 on the insulated transformer cases of transformers E and F respec- 'tively. With this arrangement, the maximum voltage between winding and case in any transformer is approximately twice that in Fig. 1. The arrangement in Fig. 2 ha. all the advantages of Fig. lwith the exception that "the-transformers 40. 4:1 and 42 would generally cost more money to build. The arrangement. however, maybe applied to inany transformers'now in use. a

it is evident that the low'voltage winding may be connected to the end of'the hi 911 voltwinding where there is a proper relation to the taps on the high voltage winding. This connection is shown in Fig. '3. 'where y; the transformers G,H and I are excited by generators 50, 51 and 52, using the'low voltage or primary windings 53, 54 and 55 of the transformers G. Hand I respectively. The low voltage windings may be grounded tot-he caseat the point of connection bet .o H V l O' fl 1 1 Amen ..e n.-1 voran e an-. 1e ow toltaae .windings. and the generator may be mounted be placed between the high and low voltage windings or at the other end of the low voltage winding, or at any point intermediate in the low voltage winding by supplying a suitable tap. It is further evident that the low voltage winding may consist of a series of windings or a number of coils in multiple or any other suitable combination common to transformer practice.

To any one familiar with the generation of very high voltages, it is evident that the improved scheme of connection permits of going to much higher voltages and capacities than is the case with the ordinary chain connection where one transformer is excited from another. Owing to the poor regulation of the ordinary chain connection, a slight change in the load or particularly in the power factor of the load causes a wide change in voltage. This tends to limit the number of transformers which can be used in a chain and also the voltage which can be generated and successfully applied. With the improved scheme, however, it is possible to go to very high voltages and high outputs, as practically the full kva. capacity of the transformer is utilized.

It is evident that where the generators are driven by suitable insulating shafts and synchronous motors, they can be held in phase even without the chain connection between transformers. For some classes of work the chain connection is not necessary once the various transformers and generators are brought into step. They will tend to remain synchronized due to the current flowing in the series. In order to facilitate matters, a regular chain connection could be utilized until the several transformers and generators were in synchronism and then the chain connection dispensed with by opening disconnecting switches 59 and 60. In this case, the chain connection and the current flowing through them after synchronism are used to maintain the several transformers in phase. It is evident that the connections shown in Figs. 1, 2 and 3 have the advantage in that the exciting end turns may have a much smaller current carrying capacity than in the case Where the usual chain connection must be depended upon for excitation. In some transformer designs this is a decided advantage.

A further advantage with the arrangements shown, is that a. resistance may be inserted in the leads between transformers. This resistance has the advantage in that it tends to damp out oscillation and protect the turns from shorting in the transformers. In the case of the ordinary chain connection, it is not possible to insert resistance of any effective magnitude owing to the fact that all of the low voltage magnetizing current must be carried through the resistance. The resistance may be used between all of the transformers and between the transformer and load or only in part as it is desired. As a comparatively small current may produce a very destructive effect or destructive rising voltage in the transformer, it is necessary to have a comparatively high resistance if a resistance is to be depended upon for protection. The arrangements, particularly that shown in Fig. 3, lend themselves very nicely to an insertion of a high resistance in the connection leads. Where the chain connection is dispensed with, the resistance may be latter where close regulation is desired for transmissions ortesting. A given series of three transformers using the ordinary chain connection has an estimated regulation of 32 percent in going from full load leading current to full load lagging current. The same" series of transformers with the improved multiple excitation under the same load conditions, has an estimated regulation or change in voltage of 1.28 percent only. The

improved connection has the same regulation I of 1.28 percent for a series of four transformers, while the same four transformers with the ordinary chain connection has an estimated regulation of 53 percent for the same changes in load.

I claim 1. In combination, a plurality of transformers each comprising a high tension and a low tension winding, said transformers having their high tension windings connected in series, said high tension windings having an end turn of one connected in parallel with an end turn of another, and means for exciting the low potential windings of each transformer.

2. In combination, a plurality of transformers each comprising a high tension and a low tension winding, said transformers having their high tension windings connected in series, one of said transformers having an end turn at the high potential end of the high tension winding thereof, connected in parallel with an end turn at the low potential end of the high tension winding of the next adjacent transformer and means for exciting the low tension windings of said transformers.

3. In combination, a plurality of transformers each comprising a high tension and a low tension winding, said transformers having their high tension windings connected in series so that'the voltages 'of said windings will be added and having an end i turn at thehigh potential end of the high tension winding of one of said transformers connected in parallel with an end turn at the low potential end of the high tension wind- 7 ingof the next adjacent transformer and an insulated alternator for supplying exciting current to said end turns. V

4. A plurality of transformers each comprising a high tension and a low tension winding, saidtransformers having their high tension windings arranged in series, the high tension winding of one of said transformers being connected to earth and the high tension Winding'of allthe transformers being grounded on. their respective cases, and an alternator for exciting the low tension winding of thetransforlner having one end of its high tension winding connected'to earth and an alternator insulated from earth for exciting the low tension winding of another of said transformers, said last named transformer having its case insulated from earth. 5. In combination, a plurality of transformers each comprising a high tension and a low tension winding, said transformers arranged in series, a transformer in said series having an end turn at the high potential end of the high tension winding thereof connected inparallel with an end turn at the low potential end of the high tension winding of the next adj acenttransformer, the high tension winding of the transformer at the low potential end of said series being connected to earth, and an alternator for supplying exciting current to the low tension winding of said end transformer and an additional. alternator insulated from earth'for exciting the low tension winding of a transformer hav- 7 ing higher potentlal position'in said series.

* r 6. A plurality of transformers having high xvi-30 tension and low tension windings, the high tension windings of the several transformers being connected in series, each of two or more of the transformers having a separate exclter energizing the low tension winding thereof, one of said exciters being insulated from ground and having a terminalthereof connected with a point. at a potential higher than a ground potential in the high tension winding circuit ofsaid transformers. I

In testimony whereof I have signed my name to this'specification on this 12th day of March A. D; 1927. r i ARTHUR OQAUSTIN. 

